1. Field of the Invention
The present invention relates to a method and apparatus for recording information on an opto-magnetic recording medium.
2. Related Background Art
As a memory system capable of recording information at a high recording density, one which uses a medium (a so-called opto-magnetic recording medium) having a recording layer made of a thin magnetic film such as MnBi, amorphous GdCo, GdFe, DyFe, GdTbFe, TbDyFe, TbFeCo, GdFeCo or GdTbFeCo has been known in the art. Such a memory is very useful in that erasure of information is easy.
For recording on the opto-magnetic recording medium, a light modulation system and a record magnetic field modulation system have been known in the art. In the light modulation system, a recording bias magnetic field is applied in a given direction and a light beam modulated with information to be recorded is irradiated on the recording medium to record the information. In the light modulation system, however, in order to update the information recorded on the recording medium, it is necessary to record new information after the recorded information has been erased. As a result, the recording speed of the memory system is low. In order to increase the recording speed, a separate erasing optical head may be provided in the recording and reproducing apparatus. However, the cost of such an apparatus is materially greater.
On the other hand, in the recording magnetic field modulation system, a non-modulated light beam of a constant intensity is irradiated on the recording medium and a recording magnetic field modulated with the information to be recorded is applied to record the information. This system does not have the disadvantage described above, but in order to increase the recording speed, it is necessary for the high frequency recording magnetic field modulated with the information applied to the recording medium to have a strength of several hundred oersteds. It is very difficult to apply such a recording magnetic field by means a simple device and a highly complex device is in fact required.